Genes Selectively Expressed in Rat Organs

Background Understanding organic functions at a molecular level is important for scientists to unveil the disease mechanism and to develop diagnostic or therapeutic methods. Aims The present study tried to find genes selectively expressed in 11 rat organs, including the adrenal gland, brain, colon, duodenum, heart, ileum, kidney, liver, lung, spleen, and stomach. Materials and Methods Three normal male Sprague-Dawley (SD) rats were anesthetized, their organs mentioned above were harvested, and RNA in the fresh organs was extracted. Purified RNA was reversely transcribed and sequenced using the Solexa high-throughput sequencing technique. The abundance of a gene was measured by the expected value of fragments per kilobase of transcript sequence per million base pairs sequenced (FPKM). Genes in organs with the highest expression level were sought out and compared with their median value in organs. If a gene in the highest expressed organ was significantly different (p < 0.05) from that in the medianly expressed organ, accompanied by q value < 0.05, and accounted for more than 70% of the total abundance, the gene was assumed as the selective gene in the organ. Results & Discussion The Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Ontology (GO) pathways were enriched by the highest expressed genes. Based on the criterion, 1,406 selective genes were screened out, 1,283 of which were described in the gene bank and 123 of which were waiting to be described. KEGG and GO pathways in the organs were partly confirmed by the known understandings and a good portion of the pathways needed further investigation. Conclusion The novel selective genes and organic functional pathways are useful for scientists to unveil the mechanisms of the organs at the molecular level, and the selective genes’ products are candidate disease markers for organs.


INTRODUCTION
It was once believed that all somatic cells shared the same genome because all of a creature's cells and organs develop from a fertilized egg.The expression of an animal's genome controls the animal's functions, whose functions are executed by its cells.Therefore, cells have different functions depending on different gene expression profiles [1,2], and so do different tissues and organs.The other gene expression profiles will doom cell differentiation [3], organ development [4], and its functions.Based on the understanding, it can be assumed that some genes as constructive ones must be universally expressed in all the cells with a nucleus, and some could be selectively expressed in cells, tissues, and organs at different developmental stages [5,6].At an animal's adulthood, its gene expression profiles could 1875-5488/ 24 be relatively stable to maintain its biological functions, and the gene expression profile would reflect its function.Therefore, the products (RNAs and proteins) from the gene selectively expressed in an organ suggest its function(s).
Health and disease are the eternal themes of humans, and are usually related to gene expression profiles.The mechanism study on human health and disease is generally carried on model animals at first, then on humans.Among them, adult rats and mice are model animals most frequently used by scientists, and no animals are studied more deeply than them.Therefore, it is a good strategy to understand humans by investigating gene expression profiles in rats.Identifying molecular targets and disease markers from rats and mice is usually the first step to understanding human health and disease, then to finding therapeutic strategies and methods.The selective gene products released into the blood can be used as damage markers.However, it is a big premise to understand the normal model animal's biological features at the molecular level before scientists comprehensively understand human health and disease [7].There were much data from animals suggesting that some genes selectively expressed in organs, e.g.NeuN (Rbfox3) in the brain or neuron [8] though with alternative opinions [9], troponin (Tnnc1, Tnni3) in the heart [10], glutamic pyruvic transaminase (GPT, Gpt) in the liver [11], and neutrophil gelatinaseassociated lipocalin (NGAL) in the kidney [12].The findings are very useful and even were adopted for clinic diagnosis and treatment.The gene products selectively and originally distributed can be used as molecular organic markers and then make disease diagnosis more accurate or earlier.Nevertheless, in the background of precision medicine [13], the selective gene products in organs are still insufficient for clinical practice, and it is still necessary to systematically screen the genes selectively expressed in organs.
Proteins and RNAs are the end products of genes and execute their functions.To identify the selective functions at the molecular level, all the selectively distributed proteins in organs should be screened out.However, among them, protein screening is a big economic burden because the study would consume plenty of antibodies.Since proteins and RNAs were transcribed and even then translated from genes, the present study would apply high-throughput sequencing technology to analyze gene expression profiles of 11 organs, including the adrenal gland, brain, colon, duodenum, heart, ileum, kidney, liver, lung, spleen, and stomach, at the RNA level, and then, based on the results, to find the likely organic markers and analyze the functional pathways the selective genes would be involved in.

Materials
Adult male Sprague-Dawley (SD) rats (age, 45 days; body weight, 180-220 g) were obtained from Chengdu Dossy Experimental Animal Co. Ltd., Chengdu, China [Certification No. SCXK (Chuan) 2008 -24].TRIzol Plus RNA Purification kit was purchased from Invitrogen (Carlsbad, CA, USA).Ultra-pure water was produced with a Milli Q water purification system manufactured by EMD Millipore Group (Darmstadt, Germany).NanoDrop ND-1000 spectrophotometer was manufactured by PeqLab (Erlangen, Germany).The multimicroplate reader of Infinite 200pro was manufactured by Tecan Group (Mannedorf, Switzerland).Other instruments or reagents used in the present study were made in China if not mentioned.

Animal Treatment
Three rats were normally treated for three days.Then, the animals were intraperitoneally anesthetized with urethane (1.0 g/kg).The rats' chests and abdomens were opened, and their organs were harvested, including the adrenal gland (Ad), brain (frontal cortex) (Br), colon (Co), duodenum (the first 5 cm) (Du), heart (left ventricle) (He), ileum (the end 5 cm) (Il), kidney (right) (Ki), liver (Li), lung (right) (Lu), spleen (Sp), and stomach (gastric antrum) (St).The tunica and mesentery of the organs were removed clearly.All the organs were frozen with liquid nitrogen and kept at -80°C by dry ice to keep them fresh, and then sent to Sangon Biotech Co. Ltd. (Shanghai China) (https:// www.sangon.com/)immediately for high-throughput sequencing.
The animal experiments were approved by the Animal Care and Use Committee of Yunnan Provincial Key Laboratory of Molecular Biology for Sinomedicine (Approved No. LL-20171023-01), Yunnan University of Traditional Chinese Medicine.

High-throughput Sequencing of mRNA
The fresh organs were frozen with liquid nitrogen and ground to powder.The total RNA in the powder was extracted and purified using the TRIzol Plus RNA Purification kit (Invitrogen, Carlsbad, CA, USA).The quantity and quality of RNA were measured by the NanoDrop ND-1000 spectrophotometer.RNA integrity was assessed by three bands (28S, 18S, and 5S) using formaldehyde denaturing agarose gel electrophoresis RNA as previously described [14,15].
Similar to the results of our previous study [16], doublestranded cDNA (ds-cDNA) was reversely transcribed from the total RNA using a SuperScript ds-cDNA synthesis kit (Invitrogen, Carlsbad, USA) in the presence of 100 pmol/L oligo dT primers.Solexa high-throughput sequencing technique was used to sequence the cDNA by Sangon Biotech Co. Ltd. (Shanghai, China).The raw data containing reads of 150 bases of nucleotide in fastq format was transformed to original sequences in fasta format by Seqkit software in the disc operation system (DOS) model [17].The sequences that matched 27 bp or more to the rat's reference mRNA sequences (https://www.ncbi.nlm.nih.gov/) were screened out by TBtools software (v0.664445552).The expected value of fragments per kilobase of transcript sequence per million base pairs sequenced (FPKM) was used for the normalization of expression level [18].

Screening Genes Selectively Expressed
Values of gene's FPKM in every organ were collected.The overall function of the organs at the gene expression level was analyzed by cluster analysis.The distance between organs was calculated by the Vegan package of Bray curtis method [19], and the cluster tree was established by Hcluster [20].
Based on the assumption that a gene is significantly overexpressed in an organ (statistical consideration), if its expression abundance accounts for the majority of that in all organs, say more than 70%, the gene is considered to be selectively expressed in that organ.The maximum FPKM value of a gene in any organs less than 5 was ignored because the expression level of the gene was supposed to be too low to analyze.Genes with FPKM above 5 were further analyzed.The means of a gene's FPKM in all the organs were sorted.The organ with the median value and those with the biggest value were selected.Then, the expression level of the gene in the two organs (the highest and median organs) was compared with the Student t-test.The q-value, a false-discovery rate alternative to p-values, was also calculated as an adjustment for multiple comparisons [21].If pvalue and q-value were both less than 0.05, the gene was regarded as a candidate gene selectively expressed in the organ.
The means of the gene in all the organs were summed up as "Total".The mean of the gene in the organ highest expressed it was regarded as "max mean".Then, the MT ratio ((max mean)/total) was calculated.If the MT ratio was above 0.7, the gene was regarded as a selective gene in the organ.The gene's product in the organ was regarded as an organic marker that may execute the selective function of the organ.The last reports on the relationship between the selective genes and the organs were searched at PubMed (www.pubmed.gov) on June 10, 2023.
The last report of the selective gene from the PubMed database was sought in the relative organ by searching the gene name and the organ both in the fields of title or abstract.

KEGG, and GO Analysis
The values of a gene in all the organs were sorted by its mean, and the organ that expressed the median value and that expressed the biggest value were selected.The expression abundance of the gene in the two organs was compared with the Student t-test.If there was significance (p < 0.05), the gene in the organ was regarded as an interesting gene.Interesting genes expressed in an organ were further analyzed to enrich the selective Kyoto Encyclopedia of Genes and Genomes (KEGG, https://www.kegg.jp/)and Gene Ontology (GO, http://www.geneontology.org/)pathways.KEGG enrichment [22] and KOG enrichment [23,24] were performed by ClusterProfiler [25].GO [26,27] enrichment was performed by TopGO.The p-value and q-value were also calculated using the software mentioned above.

Total FPKM Distribution
In the normal rats, 32,623 genes' transcripts were detected, and most genes were expressed at a very low level (FPKM < 1), only a small portion of genes expressed at a very high level (FPKM > 1000) (Fig. 1A).The overall FPKM distribution of every organ was similar.However, organs' function is believed to be different, which suggests that the gene most highly expressed in one organ could be different from that in the other.According to the results of cluster analysis at the expression level (Fig. 1B), the function of the colon is near the ileum, then to the duodenum and stomach, which is easy to be understood.The function of the kidney is near to the adrenal gland, then to the heart and brain; and the spleen's function is near to the lung.To our surprise, the function of the liver was far from that of the other organs.

Fig. (2).
Genes selectively expressed in different organs based on their abundance.Abbreviations: Ad, adrenal gland; Br, brain; Co, colon; Du, duodenum; He, heart; Il, ileum; Ki, kidney; Li, liver; Lu, lung; Sp, spleen; St, stomach.(A higher resolution / colour version of this figure is available in the electronic copy of the article).

Genes with Description Selectively Expressed in Different Organs
There were 15,922 genes with FPKM in any organ above 5, and 14,115 genes were significantly (p < 0.05) highly expressed in an organ.Among them, there were 12,617 genes accepted with q < 0.05.Apart from 123 genes without description, there were 1,283 genes with description selectively expressed in 11 organs (Fig. 2).From the results from Fig. (2), the brain (Br) was the organ with the most complex function because 459 genes were selectively expressed in it.Instead, the gastrointestinal tracts, including the stomach (St), duodenum (Du), ileum (Il), and colon (Co), selectively expressed fewer genes, suggesting that their functions could be relatively simple or similar to other organs.
The total genes selectively expressed or the top 20 (if more) in 11 organs are listed in Tables 1-11.Their full lists can be seen in the supplementary data.According to the description of the gene name, most selective genes were associated with the known specific functions of the organ.For example, Mgarp (mitochondria-localized glutamic acid-rich protein) in the adrenal gland (Table 1) is associated with steroidogenesis [28]; Scg3 (secretogranin III) in the brain (Table 2) with neuroendocrine [29]; Reg3g (regenerating islet-derived 3 gamma) in the colon (Table 3) with intestinal bacterial translocation to the mesenteric lymph nodes [30];        Gip (gastric inhibitory polypeptide) in the duodenum (Table 4) with regulation of insulin secretion [31]; Klhl38 (kelchlike family member 38) in the heart (Table 5), though seldom reported, could be associated with the reversion of striated muscle atrophy [32]; Defa24 (defensin alpha 24) in the ileum (Table 6) with intestinal barrier [33]; Slc3a1 [solute carrier family 3 (amino acid transporter heavy chain), member 1] in the kidney (Table 7) with the transport of cystine and other amino acids across the membrane [34]; C5 (hemo-lytic complement) in the liver (Table 8) was early verified to execute innate immune [35]; Icam1 (intercellular adhesion molecule 1) in the lung (Table 9) with innate immune [36]; Coch (cochlin) used to highly expressed in the inner ear [37] also highly expressed in the spleen (Table 10); and Cxcl17 (chemokine (C-X-C motif) ligand 17) in the stomach (Table 11) with its innate immune [38].Nevertheless, there were many genes that were not reported in the relative organs (supplementary data).

KEGG Pathway Enrichment
KEGG is a bioinformatics database resource for understanding high-level functions and utilities of the biological system, which includes the cell, the organism, and the ecosystem, from molecular-level information, especially largescale molecular datasets generated by genome sequencing and other high-throughput experimental technologies.The selective KEGG pathways were enriched based on the abundance of genes most highly expressed in organs.The number of the selective pathway is listed in Fig. (3) and the top 20 pathways are listed in Tables 12-22.Their full lists can be seen in the supplementary data.There were 179 "selective" pathways in 11 rat organs.Among them, 52 pathways were involved in two organs, 7 in three organs, and 1 in four organs.It should be noted that the "selective" pathways engaged in two or more organs were based on enrichment analysis.As can be seen from Fig. (3), organs with many selective pathways, like the brain, indicate that they undertake many complex functions.Conversely, organs with few selective pathways, like the adrenal glands and stomach, indicate their relatively simple functions.The results in Fig. (3), suggested that the lung could be the top 2 organs with the complex functions of the 11 organs.

(A higher resolution / colour version of this figure is available in the electronic copy of the article).
The function of some pathways was verified in relative organs based on common understandings, for example, ko04925 (Aldosterone synthesis and secretion) in the adrenal gland (Table 12), ko04721 (Synaptic vesicle cycle) in the brain (Table 13), ko04672 (Intestinal immune network for IgA production) in the colon (Table 14), ko04975 (Fat digestion and absorption) in the duodenum (Table 15), ko04260 (Cardiac muscle contraction) in the heart (Table 16), ko00520 (Amino sugar and nucleotide sugar metabolism) in the ileum (Table 17), ko04964 (Proximal tubule bicarbonate reclamation) in the kidney (Table 18), ko04976 (Bile secretion) in the liver (Table 19), ko04151 (PI3K-Akt signaling pathway) in the lung (Table 20), ko04640 (Hematopoietic cell lineage) in the spleen (Table 21), and ko04971 (Gastric acid secretion) in the stomach (Table 22).

GO Pathway Enrichment
The GO database is the world's largest source of bioinformation on the functions of genes.This knowledge of the genes is a foundation for computational analysis of large-scale molecular biology and genetics experiments in biomedical research.Selective GO pathways were enriched based on the abundance of genes most highly expressed in organs.The number of the selective pathway is listed in Fig. (4) and the pathways of the adrenal gland, brain, colon, duodenum, heart, ileum, kidney, liver, lung, spleen, and stomach are listed in Tables 23-33, respectively.There were 4,432 relatively selective pathways in 11 rat organs.Among them, 971 pathways were involved in two organs, 357 in three organs, 86 in four organs, 21 in five organs, 7 in six organs, and 1 in seven organs.It should be noted that the "selective" pathways are involved in two or more organs based on the enrichment analysis.
As can be seen from Fig. (4), organs with many selective pathways, like the lung, spleen and brain, indicate that they undertake many complex functions.Conversely, organs with few selective pathways, like the stomach and adrenal glands, indicate their relative sample functions.The results in Fig. (3), is similar to those in Fig. (4).
The top 20 GO pathways are shown in Tables 23-33, and their full lists can be seen in the supplementary data.As for the top 20 GO pathways, the adrenal gland (Table 23), colon (Table 25), and kidney (Table 29) had no real selective pathways, and the brain had the most selective pathways, suggesting that the brain has specific functions (Table 24).Note: * also significantly expressed in other organs.Sorted by q-value.
According to the results of GO enrichment, the adrenal gland is a hypermetabolic organ because mitochondria in the organ are very active (Table 23); the brain is a neural organ (Table 24), which is well-accepted by scientists; the colon is an immune and metabolic organ (Table 25); the duodenum is mainly an immune organ (Table 26); the heart is also a hypermetabolic organ (Table 27); the ileum is primarily an organ associated with protein synthesis, immune, and digestion (Table 28); the kidney (Table 29) and liver (Table 30) are mainly an organ associated with metabolism; the lung is an organ mainly associated with angiogenesis and blood circulation (Table 31); the spleen is an organ mainly associated with organelle metabolism (Table 32), and the stomach is an organ mainly associated with digestion and glandular secretion (Table 33).

Genes without Description but Selectively Expressed
Apart from the genes whose function is described, there were 123 genes without a clear description but selectively expressed in 11 organs (Fig. 5).From the results of Fig. ( 5), most genes without description were selectively expressed in the adrenal gland and brain.Instead, there were fewer genes without description in rat gastrointestinal tracts, including stomach, duodenum, ileum, and colon.The top 20 genes without description in the adrenal gland, brain, colon, duodenum, heart, ileum, kidney, liver, lung, spleen, and stomach were listed in Tables 34-44, respectively; and their full lists can be seen in the supplementary data.Because the genes were not described but selectively expressed in the organs, their products and functions need further investigation.Given the low number of genes selectively expressed in the adrenal gland, the high number of undescribed high expression of genes in this organ suggests that the organ may be less studied.

DISCUSSION
Screening selectively expressed genes in organs is not only a tough task but also meaningful work because the results of the work will provide useful clues and even evidence for scientists to unveil the mechanism behind the overall dysfunction and symptoms.At least, we can obtain the putative organic markers for evaluating organic injury.Note: * also significantly expressed in other organs.Sorted by q-value.
There were good examples of some proteins selectively expressed in organs that were used as disease markers [8,[10][11][12] or used as therapeutic targets like trastuzumab on HER2 to treat breast cancer [167].However, many selective genes have still not been revealed.The present study screened out 1,406 genes selectively expressed in 11 rat organs, among which, 1,283 genes' function was described, and 123 of which still need to be described in the near future.Some of the genes' function was confirmed in the organs that were noted in Tables 1-11, but a good portion of them or the relationship between their function and the organs was not addressed.The new findings are useful to unveil the mechanism of their organic functions.Unfortunately, as for the selective genes in organs mentioned in the introduction, only troponin [10] was proved to be selective by the present study, and NeuN in the brain [8], GPT in the liver [11], and NGAL in the kidney [12] were not included in the present list of the selective genes.After consulting the FPKM values, it is exactly that the FPKM of NeuN in the brain was the highest, but not significant.The relative neuronal marker was further proved by recent work [9].The highest GPT (GPT2) in the liver was significant, but the level of expression was not dominant (only about 45% of the total).Of course, if the criterion of selective genes was lowered, more genes would be included in the selective gene list, namely, in the list of putative organic markers.Phosphodiesterase 5 (PDE5a), an enzyme associated with angiectasis, is another similar example.PDE5a was verified to be the most highly expressed gene in the lung, but not included in the selective gene list (Table 9), supporting PDE5 inhibitors' pharmacological effect on pulmonary arterial hypertension [168,169].Note: Sorted by q-value.Ad, adrenal gland; Du, duodenum The selective genes and their products can be used as physiological or disease markers.If a cell is injured, the selective gene's product normally existing in its cytoplasm will be released to the blood.Based on the principle, some injury markers like serum Myl3 protein for heart injury [170] were screened out and verified by the present study.Theoretically, products from selective genes can be used as disease markers.However, it should be noted that because of some genes expressed in rats (e.g., Uox in the liver) [171], but not in humans, the fact that the products from the selective genes used as disease markers are only advisory, needing further verification.
The functional pathways of an organ enriched by the highest-expressed genes were largely supported by the known understanding.However, there are still some interesting functions that were not focused on.For example, KEGG pathways (Tables 12-22) like ko00061 (fatty acid biosynthesis) in the adrenal gland, ko04911 (insulin secretion) in the brain, ko00280 (Valine, leucine, and isoleucine degradation) in the heart and kidney, and ko04360 (axon guidance) in the lung were seldom paid attention to by scientists.Similar results would be obtained in the results of GO pathways (Table 23-33).The unpopular organic functional pathways enriched by the present study would open a new window to make insight into their mechanism.Especially the adrenal glands may be an organ with few basic researches.
Though the selective genes and the interesting genes only existed in one organ, the organic pathways including KEGG (Tables 12-22) and GO (Tables 23-33) pathways, enriched by them could exist in two or more organs.Since a pathway often involves many proteins, it is theoretically different for the real functions of the same selective pathway enriched by different selective genes.The same pathway is enriched in different organs with different profiles.Anyway, the functions are different from organ to organ, although they share some similarities at pathway levels.

CONCLUSION
In the end, because there were no standard criteria ready to evaluate a gene's selectivity, the present study used the dominant portion of FPKM value and statistical analysis.If the FPKM value of a gene in an organ accounted for 70% of the total values of all the organs concerned, the gene was assumed as the selective gene in the organ after excluding genes with low abundance.If the criterion were lowered, the list of the selective genes would be lengthened.On the other hand, the selective genes screened out by the present study were only based on the results of 11 organs in male rats, and some selective genes in other organs or female rats were neglected or missed.Moreover, the weights of the organs were not taken into account in the present study.Considering that the genome of rats has approximately 85% similarity with that of humans, this study provides a useful exploration of human organic markers and organ function, though the selective genes, the putative markers, and the functional pathways suggested are only advisory and worthy of further investigation.

AUTHORS' CONTRIBUTIONS
It is hereby acknowledged that all authors have accepted responsibility for the manuscript's content and consented to its submission.They have meticulously reviewed all results and unanimously approved the final version of the manuscript.

ETHICS APPROVAL AND CONSENT TO PARTICI-PATE
The animal experiments were approved by the Animal Care and Use Committee of Yunnan Provincial Key Laboratory of Molecular Biology for Sinomedicine (Approved No. LL-20171023-01), Yunnan University of Traditional Chinese Medicine, Kunming, Yunnan, China.

HUMAN AND ANIMAL RIGHTS
All the animal experimentation was performed according to the Guide for the CARE and USE of Laboratory Animals and ARRIVE guidelines.

CONSENT FOR PUBLICATION
Not applicable.

Fig. ( 1 ).
Fig. (1).Distribution of gene expression and clustering analysis was made from 32,623 genes' transcripts detected.The distribution of gene expression in different organs was similar (Mean ± SD, n = 3) (A).However, the function of the organs was different based on the clustering analysis of total gene expression from 11 organs (n = 3) (B).Abbreviations: Ad, adrenal gland; Br, brain; Co, colon; Du, duodenum; He, heart; Il, ileum; Ki, kidney; Li, liver; Lu, lung; Sp, spleen; St, stomach.(A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. ( 4
Fig. (4).Selective GO enrichment in different organs based on the abundance of genes most highly expressed in organs.Abbreviations: Ad, adrenal gland; Br, brain; Co, colon; Du, duodenum; He, heart; Il, ileum; Ki, kidney; Li, liver; Lu, lung; Sp, spleen; St, stomach.(A higher resolution / colour version of this figure is available in the electronic copy of the article).

Table 1 . Top 20 of 40 genes with description selectively expressed in the adrenal gland (Ad) based on their abundance (n = 3).
Note: Sorted by q-value.Br, brain; Co, colon; Du, duodenum; He, heart; Ki, kidney; Lu, lung; St, stomach * Last Ref. was based on the reports documented in PubMed (www.pubmed.gov)before June 10, 2023.

Table 2 . Top 20 of 459 genes with description selectively expressed in the brain (Br) based on their abundance (n = 3).
Last Ref. was based on the reports documented in PubMed (www.pubmed.gov)before June 10, 2023.

Table 9 . Top 20 of 122 genes with description selectively expressed in rat lung
(Lu) based on their abundance (n = 3).

Table 10 . Top 20 of 102 genes with description selectively expressed in the spleen (Sp) based on their abundance (n = 3).
Note: Sorted by q-value.Ad, adrenal gland; Br, brain; Du, duodenum; He, heart; Il, ileum; Ki, kidney; St, stomach * Last Ref. was based on the reports documented in PubMed (www.pubmed.gov)before June 10, 2023.

Table 12 . Selective KEGG pathways in the adrenal gland.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 13 . Top 20 of 50 Selective KEGG pathways in the brain.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 14 . Selective KEGG pathways in the colon.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 15 . Selective KEGG pathways in the duodenum.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 16 . Top 20 of 21 Selective KEGG pathways in the heart.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 17 . Selective KEGG pathways in the ileum.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 18 . Top 20 of 23 selective KEGG pathways in the kidney.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 19 . Top 20 of 34 selective KEGG pathways in the liver.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 20 . Top 20 of 46 Selective KEGG pathways in the lung.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 21 . Top 20 of 33 selective KEGG pathways in the spleen.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 22 . Selective KEGG pathways in the stomach.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 23 . Top 20 of 122 selective GO pathways in the adrenal gland.
). Selective GO enrichment in different organs based on the abundance of genes most highly expressed in organs.

Table 24 . Top 20 of 897 selective GO pathways in the brain.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 25 . Top 20 of 536 selective GO pathways in the colon.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 26 . Top 20 of 171 selective GO pathways in the duodenum.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 27 . Top 20 of 554 selective GO pathways in the heart.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 28 . Top 20 of 141 selective GO pathways in the ileum.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 31 . Top 20 of 1389 selective GO pathways in the lung.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 32 . Top 20 of 1168 selective GO pathways in the spleen.
* also significantly expressed in other organs.Sorted by q-value. Note:

Table 33 . Top 20 of 21 selective GO pathways in the stomach.
Note: * also significantly expressed in other organs.Sorted by q-value.

Table 34 . The top 20/32 genes were not described but selectively expressed in the adrenal glands based on their abundance (n = 3).
Note: Sorted by q-value.Du, duodenum; Il, ileum; Sp, spleen; St, stomach Ad

Table 36 . Genes were not described but selectively expressed in the colon based on their abundance (n = 3). No. Gene ID Gene Name Median Organ FPKM p-value q-value Mean/ total Mean Total
Note: Sorted by q-value.Ad, adrenal gland; St, stomach

Table 38 . Genes were not described but selectively expressed in the heart based on their abundance (n = 3).
Note: Sorted by q-value.Ad, adrenal gland; Co, colon; Du, duodenum; Il, ileum; Ki, kidney; Li, liver; St, stomach

Table 39 . Genes were not described but selectively expressed in the ileum based on their abundance (n = 3).
Note: Sorted by q-value.Ad, adrenal gland; Lu, lung

Table 40 . Genes were not described but selectively expressed in the kidney based on their abundance (n = 3).
Note: Sorted by q-value.Ad, adrenal gland; Br, brain; He, heart; Lu, lung; Sp, spleen; St, stomach

Table 41 . Genes were not described but selectively expressed in the liver based on their abundance (n = 3).
Sorted by q-value.Ad, adrenal gland;Du, duodenum Note:

Table 42 . Genes were not described but selectively expressed in the lung based on their abundance (n = 3).
Note: Sorted by q-value.Ad, adrenal gland; He, heart; Ki, kidney; St, stomach

Table 43 . Genes were not described but selectively expressed in the spleen based on their abundance (n = 3). No. Gene ID Gene Name Median Organ FPKM p-value q-value Mean/ total Mean Total
Note: Sorted by q-value.Ad, adrenal gland; Du, duodenum; Ki, kidney; Lu, lung; St, stomach